2 minutes ago, studiot said:

The wave function of a photon extends over all space and time.

How long does a rocket take to travel a distance of 5 lightyears with 99.999%c?

Both your questions are incompatible with balancing or trading off motion through space against motion through time.

The solution is that the interval is measured along what is known as a world line, which is a four dimensional space curve.

That is a curve like say a spring in 3 dimensions, which is a helix, but in four dimensions 3 space and one of Time.

As an aside other combinations of different numbers of space and time dimensions have been considered in the past, by the man who proved relativity experimentally - Eddington.

17 minutes ago, Rudolf said:

How much distance and time does photon travels (on his own clock) to travel a distance over 5 lightyears between 2 stars?

As far as I know there is no inertial frame in which a photon is at rest, and questions about "on his own clock" or what a photon “experiences” do not make physical sense.

13 minutes ago, Rudolf said:

How long does a rocket take to travel a distance of 5 lightyears with 99.999%c?

3 minutes ago, studiot said:

Both your questions are incompatible with balancing or trading off motion through space against motion through time.

The solution is that the interval is measured along what is known as a world line, which is a four dimensional space curve.

That is a curve like say a spring in 3 dimensions, which is a helix, but in four dimensions 3 space and one of Time.

As an aside other combinations of different numbers of space and time dimensions have been considered in the past, by the man who proved relativity experimentally - Eddington.

That is not really an answer to the question, I think it should be more like this:

To answer how long this trip takes, we have to look at it from two different perspectives due to Einstein's theory of special relativity: from Earth, the trip takes just over 5 years, but for the astronauts inside the rocket, it takes only about 8.17 days.

3 minutes ago, Rudolf said:

That is not really an answer to the question, I think it should be more like this:

To answer how long this trip takes, we have to look at it from two different perspectives due to Einstein's theory of special relativity: from Earth, the trip takes just over 5 years, but for the astronauts inside the rocket, it takes only about 8.17 days.

So what conclusion do you draw from that ?

20 hours ago, Rudolf said:

The two are not independent, but complementary aspects of a single process: the more an object moves through space, the less it moves through time, while its total motion through spacetime remains unchanged.

And in particular how does the above calculation not conflict with what you said correctly earlier ?

I repeat the world line is the appropriate measurement.

So the next question should be what is the world line comprised of and how do we measure it?

Edited Friday at 01:47 PM3 days by studiot

20 minutes ago, Ghideon said:

As far as I know there is no inertial frame in which a photon is at rest, and questions about "on his own clock" or what a photon “experiences” do not make physical sense.

I do agree, so that´s why I prefer to use a rocket as an example traveling at 99.999%c traveling between 2 (A - B ) stars with a distance of 5 lightyears between each other.

While the time at star A and B will be more than 5 years, the rocket will travel from A to B in less than 5 years.

We only can imagine that the time at light speed it would be 0 secondes to travel this distance. In a very extreme situation you might argue that it would take only 1 second if you travel near light speed over a distance of 5 lightyears.

16 minutes ago, studiot said:

So what conclusion do you draw from that ?

And in particular how does the above calculation not conflict with what you said correctly earlier ?

All matter always travel with the velocity of light. By changing our speed we only change the velocity of time. But this never will be zero.

16 minutes ago, Rudolf said:

I do agree, so that´s why I prefer to use a rocket as an example traveling at 99.999%c traveling between 2 (A - B ) stars with a distance of 5 lightyears between each other.

While the time at star A and B will be more than 5 years, the rocket will travel from A to B in less than 5 years.

We only can imagine that the time at light speed it would be 0 secondes to travel this distance. In a very extreme situation you might argue that it would take only 1 second if you travel near light speed over a distance of 5 lightyears.

All matter always travel with the velocity of light. By changing our speed we only change the velocity of time. But this never will be zero.

How do you define a lightyear ?

Please think again if you genuinely think that Special Relativity allows 'matter' to travel at travel at lightspeed or so close that it traverses 5 lightyears in one second.

23 hours ago, studiot said:

How do you define a lightyear ?

Please think again if you genuinely think that Special Relativity allows 'matter' to travel at travel at lightspeed or so close that it traverses 5 lightyears in one second.

"A light-year is usually interpreted as the distance light travels in one year. I propose an alternative interpretation: what we call a light-year is actually the distance that our own frame advances relative to the propagation of light. In that view, we are measuring our own motion through spacetime rather than the motion of light through space."

21 hours ago, Rudolf said:

"A light-year is usually interpreted as the distance light travels in one year. I propose an alternative interpretation: what we call a light-year is actually the distance that our own frame advances relative to the propagation of light. In that view, we are measuring our own motion through spacetime rather than the motion of light through space."

What distance function (metric) are you employing in making this play upon words ?

5 hours ago, studiot said:

What distance function (metric) are you employing in making this play upon words ?

I will argue that distances are differences in time.

We experience reality with a delay of 1sec per 300.000km. Your own moment in time "now" is the exact point from where reality is created.

4 hours ago, Rudolf said:

I will argue that distances are differences in time.

We experience reality with a delay of 1sec per 300.000km. Your own moment in time "now" is the exact point from where reality is created.

More play upon words in place of an answer to the question I asked.

Please define your words more specifically.

I can't see how you can get far in the scientific world if you keep using different definitions from everybody else.

On 6/26/2026 at 2:23 PM, Rudolf said:

How long does a rocket take to travel a distance of 5 lightyears with 99.999%c?

Before you told me you define a lightyear as a distance.

Now you tell me you define it as a difference in time.

How is this playing around not self contradictory ?

On 6/26/2026 at 9:23 AM, Rudolf said:

How long does a rocket take to travel a distance of 5 lightyears with 99.999%c?

According to which observer? Relativity only allows you to make statements about invariant quantities without specifying what a quantity is relative to.